1. Field of Invention
The invention relates generally to the field of oil and gas production. More specifically, the present invention relates to a perforating system having signal circuit connectors on adjacent members of a perforating string that can be put into direct contact.
2. Description of Prior Art
Perforating systems are used for the purpose, among others, of making hydraulic communication passages, called perforations, in wellbores drilled through earth formations so that predetermined zones of the earth formations can be hydraulically connected to the wellbore. Perforations are needed because wellbores are typically completed by coaxially inserting a pipe or casing into the wellbore. The casing is retained in the wellbore by pumping cement into the annular space between the wellbore and the casing. The cemented casing is provided in the wellbore for the specific purpose of hydraulically isolating from each other the various earth formations penetrated by the wellbore.
Perforating systems typically comprise one or more perforating guns strung together, these strings of guns can sometimes surpass a thousand feet of perforating length. In FIG. 1 an example of a perforating system 11 is shown having a perforating gun string 4 with perforating guns 6 coupled together by connector subs 13. The gun string 4 is shown disposed within a wellbore 1 on a wireline 5. The perforating system 11 as shown also includes a service truck 7 on the surface 9, where in addition to providing a raising and lowering means, the wireline 5 also provides communication and control connectivity between the truck 7 and the perforating gun 6. The wireline 5 is threaded through pulleys 3 supported above the wellbore 1. As is known, derricks, slips and other similar systems may be used in lieu of a surface truck for inserting and retrieving the perforating system into and from a wellbore. Moreover, perforating systems may also be disposed into a wellbore via tubing, drill pipe, slick line, coiled tubing, to mention a few.
Included with the perforating gun 6 are shaped charges 8 that typically include a housing, a liner, and a quantity of high explosive inserted between the liner and the housing. When the high explosive is detonated, the force of the detonation collapses the liner and ejects it from one end of the charge 8 at very high velocity in a pattern called a “jet” 12. The jet 12 perforates the casing and the cement and creates a perforation 10 that extends into the surrounding formation 2.
FIG. 2 is a side partial sectional view of a portion of a known perforating gun string 4 depicting an example connection between a perforating gun 6 and a connector sub 13. Also shown in FIG. 2 is an example detonation system for the shaped charges 8. The detonation system illustrated includes a detonation cord 15, that when ignited imparts a shock wave to initiate shaped charge 8 detonation. The system further includes an electrical circuit 14 that delivers electrical signals from the surface to initiators 17 for selectively igniting a specific detonation cord 15. Wire connectors 16 are shown within the circuit 14 for providing electrical communication between components within the circuit 14 and external to the circuit 14.
The circuits 14 therefore can be implemented for selective detonation of shaped charges 8 in specific perforating guns. Final assembly of the circuits 14, such as making up the wire connectors 16, is performed within the body of the guns 6. Ports 18 with removable covers are shown for accessing the circuits 14 and connectors 16. The ports 18 however may leak when exposed to high pressures downhole. Moreover, wires of the circuit 14 that pass between adjacent connector subs 13 and guns 6 can become twisted or otherwise damaged during assembly.